Chucks and clamps for holding objects of a lithographic apparatus and methods for controlling a temperature of an object held by a clamp of a lithographic apparatus

ABSTRACT

A lithographic apparatus includes a clamp ( 406 ) configured to receive an object ( 402 ). The clamp defines at least one channel ( 408 ) configured to pass a fluid at a first fluid temperature. The lithographic apparatus also includes a chuck ( 404 ) coupled to the clamp. The chuck ( 404 ) defines at least one void ( 464 ) configured to thermally insulate the chuck from the clamp.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority of U.S. Provisional Patent ApplicationNo. 62/237,732, filed on Oct. 6, 2016, and U.S. Provisional PatentApplication No. 62/271,688, filed on Dec. 28, 2016, both of which areincorporated herein in their entirety by reference.

FIELD

The present disclosure relates to chucks and clamps for holding objectsof a lithographic apparatus and methods for controlling a temperature ofan object held by a clamp of a lithographic apparatus.

BACKGROUND

A lithographic apparatus exposes a desired pattern onto a target portionof a substrate. Lithographic apparatuses can be used, for example, tomanufacture integrated circuits (ICs). In that circumstance, apatterning device, for example, a mask or a reticle, can be used togenerate a circuit pattern corresponding to an individual layer of theIC, and this pattern can be imaged onto a target portion (for example,part of one or several dies) on a substrate (for example, a siliconwafer) that has a layer of radiation-sensitive material (resist).Typically, a single substrate will contain a network of adjacent targetportions that are successively exposed. Known lithographic apparatusinclude so-called steppers, in which each target portion is irradiatedby exposing an entire pattern onto the target portion in one go, andso-called scanners, in which each target portion is irradiated byscanning the pattern through the beam in a given direction (the“scanning”-direction) while synchronously scanning the substrateparallel or anti parallel to this direction. It is also possible totransfer the pattern from the patterning device to the substrate byimprinting the pattern onto the substrate.

Lithography is widely recognized as one of the key steps in themanufacture of ICs and other devices and/or structures. However, as thedimensions of features made using lithography become smaller,lithography is becoming a more critical factor for enabling miniature ICor other devices and/or structures to be manufactured.

A theoretical estimate of the limits of pattern printing can be given bythe Rayleigh criterion for resolution as shown in equation (1):

$\begin{matrix}{{CD} = {k_{1}*\frac{\lambda}{NA}}} & (1)\end{matrix}$where λ is the wavelength of the radiation used, NA is the numericalaperture of the projection system used to print the pattern, k₁ is aprocess dependent adjustment factor, also called the Rayleigh constant,and CD is the feature size (or critical dimension) of the printedfeature. It follows from equation (1) that reduction of the minimumprintable size of features can be obtained in three ways: by shorteningthe exposure wavelength λ, by increasing the numerical aperture NA, orby decreasing the value of k₁.

To shorten the exposure wavelength and, thus, reduce the minimumprintable size, it has been proposed to use an extreme ultraviolet (EUV)radiation source. EUV radiation is electromagnetic radiation having awavelength within the range of 5-20 nm, for example within the range of13-14 nm, for example within the range of 5-10 nm such as 6.7 nm or 6.8nm. Possible sources include, for example, laser-produced plasmasources, discharge plasma sources, or sources based on synchrotronradiation provided by an electron storage ring.

The radiation generated by such sources will not, however, be only EUVradiation and the source may also emit at other wavelengths includinginfra-red (IR) radiation and deep ultra-violet (DUV) radiation. DUVradiation can be detrimental to the lithography system as it can resultin a loss of contrast. Furthermore unwanted IR radiation can cause heatdamage to components within the system. It is therefore known to use aspectral purity filter to increase the proportion of EUV in thetransmitted radiation and to reduce or even eliminate unwanted non-EUVradiation such as DUV and IR radiation.

A lithographic apparatus using EUV radiation may require that the EUVradiation beam path, or at least substantial parts of it, must be keptin vacuum during a lithographic operation. In such vacuum regions of thelithographic apparatus, a clamp may be used to clamp an object, such asa patterning device and/or a substrate, to a structure of thelithographic apparatus, such as a chuck of a patterning device tableand/or a substrate table, respectively.

In addition, a lithographic apparatus using EUV radiation may requiretemperature regulation of, for example, the patterning device and/or thesubstrate. Heat produced by the EUV radiation or the unwanted non-EUVradiation may cause deformations in, for example, the patterning deviceand/or the substrate during a lithographic operation because of the heatabsorbed by the patterning device and/or the substrate. To reduce thedeformation, a cooling fluid may be circulated through the clamp.

BRIEF SUMMARY

In some embodiments, a lithographic apparatus includes a clampconfigured to receive an object. The clamp defines at least one channelconfigured to pass a fluid at a first fluid temperature. Thelithographic apparatus also includes a chuck coupled to the clamp. Thechuck defines at least one void configured to thermally insulate thechuck from the clamp.

In some embodiments, the at least one void is at a vacuum. In otherembodiments, the at least one void is filled with a fluid.

In some embodiments, the at least one void includes a plurality ofvoids. In some embodiments, the chuck includes a plurality of burlsdefining the at least one void. The chuck can include a first layercoupled to the clamp and a second layer defining the plurality of burlsthat define the at least one void.

In some embodiments, the lithographic apparatus includes a fluidconditioning device configured to change a temperature of the firstfluid. The fluid conditioning device can be configured to change atemperature of the first fluid from a second fluid temperature to thefirst fluid temperature. The fluid conditioning device can be configuredto change the temperature of the first fluid from the second fluidtemperature to the first fluid temperature when the object is beingexposed with radiation, and the second fluid temperature is greater thanthe first fluid temperature. In some embodiments, the first fluidtemperature is in a range from about −15° C. to about 15° C., and thesecond fluid temperature is in a range from about 17° C. to about 27° C.In some embodiments, the first fluid temperature is less than a targetaverage temperature of the object when the object is being exposed withradiation.

In some embodiments, the object comprises a material having acoefficient of thermal expansion that varies as a function oftemperature, and the coefficient of thermal expansion of the material ofthe object is about zero at a zero-crossing temperature of the object.The first fluid temperature can be such that an average temperature ofthe object when the object is being exposed with radiation is equal toabout the zero-crossing temperature of the object. The first fluidtemperature can also be such that internal forces of the object when theobject is being exposed with radiation are substantially symmetric in adirection perpendicular to a surface of the clamp holding the object.The first fluid temperature can also be such that a sum of the internalforces of the object when the object is being exposed with radiation isabout equal to zero.

In some embodiments, the at least one channel comprises a plurality ofchannels, and the object is a patterning device.

In some embodiments, a method for controlling a temperature of an objectheld by a clamp of a lithographic apparatus includes exposing an objectwith radiation. The method also includes passing a fluid at a firstfluid temperature through at least one channel defined by the clamp tocondition a temperature of the clamp. The clamp is coupled to a chuckdefining at least one void configured to thermally insulate the chuckfrom the clamp.

In some embodiments, the method also includes, before passing the fluidat the first fluid temperature through the at least one channel definedby the clamp, passing the fluid at a second fluid temperature throughthe at least one channel defined by the clamp to condition thetemperature of the clamp. The method also includes, after passing thefluid at the second fluid temperature through the at least one channeldefined by the clamp, changing the second fluid temperature of the fluidto the first fluid temperature of the fluid. The second fluidtemperature is greater than the first fluid temperature.

In some embodiments, the first fluid temperature is conditioned to be ina range from about −15° C. to about 15° C., and the second fluidtemperature is conditioned to be in a range from about 17° C. to about27° C. In some embodiments, the first fluid temperature is conditionedto be about −8° C., and the second fluid temperature is conditioned tobe about 22° C. In some embodiments, the first fluid temperature isconditioned to be less than an average temperature of the object whenexposing the object with radiation.

In some embodiments, the object comprises a material having acoefficient of thermal expansion that varies as a function oftemperature, and the coefficient of thermal expansion of the material ofthe object is about zero at a zero-crossing temperature. And the passingthe fluid at the first fluid temperature through the at least onechannel generates an average temperature of the object when exposing theobject with radiation that is equal to about the zero-crossingtemperature of the material of the object.

In some embodiments, the first fluid temperature is such that internalforces of the object when the object is being exposed with radiation aresubstantially symmetric in a direction perpendicular to a surface of theclamp holding the object. In some embodiments, the first fluidtemperature is such that a sum of the internal forces of the object whenthe object is being exposed with radiation is about equal to zero. Insome embodiments, the object is a patterning device.

Further features and advantages of the embodiments, as well as thestructure and operation of various embodiments, are described in detailbelow with reference to the accompanying drawings. It is noted that theinvention is not limited to the specific embodiments described herein.Such embodiments are presented herein for illustrative purposes only.Additional embodiments will be apparent to persons skilled in therelevant art(s) based on the teachings contained herein.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

The accompanying drawings, which are incorporated herein and form partof the specification, illustrate the present invention and, togetherwith the description, further serve to explain the principles of theembodiments and to enable a person skilled in the relevant art(s) tomake and use the invention.

FIG. 1 is a schematic illustration of a reflective lithographicapparatus, according to an embodiment.

FIG. 2 is a schematic illustration of a reflective lithographicapparatus, according to another embodiment.

FIG. 3 is a schematic illustration of a cross-sectional view of a chuckand a clamp holding an object, according to an embodiment.

FIG. 4 illustrates a top diagram charting the exposure power of aradiation beam incident on an object as a function of time, and a bottomdiagram charting the temperature of cooling fluid passing throughseparate channels of a clamp as a function of time, according to anembodiment.

FIG. 5 illustrates a diagram charting the coefficient of thermalexpansion of a material that varies as a function of temperature,according to an embodiment.

FIG. 6 illustrates a diagram charting the generated internal forces ofan object comprising a material with a temperature-dependent coefficientof thermal expansion (as shown in FIG. 5) as a function of temperature,according to an embodiment.

FIG. 7 charts the temperature of an object and the clamp along adirection perpendicular to the exposure surface of the object at variouspoints in time, according to an embodiment.

FIG. 8 illustrates a diagram illustrating the generated internal forcesof an object comprising a material having a temperature-dependentcoefficient of thermal expansion as shown in FIG. 5 and a temperaturedistribution as shown in FIG. 7, according to an embodiment.

FIG. 9 is a cross-sectional view of the chuck and the clamp holding theobject of FIG. 3, schematically showing the generated internal forcesgenerated by a temperature distribution as shown in FIG. 8, according toanother embodiment.

FIG. 10 charts the raw overlay error of a pattern exposed on a substrateat various points in time, according to an embodiment.

FIG. 11 charts the raw overlay error of a pattern exposed on a substrateat various points in time, according to another embodiment.

FIG. 12 is a schematic illustration of a cross-sectional view of thechuck and the clamp holding the object of FIG. 3 with a pellicle,according to an embodiment.

FIG. 13 charts the temperature of a surface of the object in FIG. 12exposed to radiation at various points in time, according to anembodiment.

FIG. 14 illustrates a diagram illustrating the generated internalthermal forces of an object comprising a material having atemperature-dependent coefficient of thermal expansion and azero-crossing temperature greater than the temperature of the object atan undeformed state, according to an embodiment.

FIG. 15 is a schematic illustration of a cross-sectional view of a clampholding an object, according to an embodiment.

FIG. 16 is a schematic illustration of a cross-sectional view of a chuckand clamp holding an object, according to another embodiment.

The features and advantages of the present invention will become moreapparent from the detailed description set forth below when taken inconjunction with the drawings, in which like reference charactersidentify corresponding elements throughout. In the drawings, likereference numbers generally indicate identical, functionally similar,and/or structurally similar elements. The drawing in which an elementfirst appears is indicated by the leftmost digit(s) in the correspondingreference number. Unless otherwise indicated, the drawings providedthroughout the disclosure should not be interpreted as to-scaledrawings.

DETAILED DESCRIPTION

This specification discloses one or more embodiments that incorporatethe features of this invention. The disclosed embodiment(s) merelyexemplify the invention. The scope of the invention is not limited tothe disclosed embodiment(s). The invention is defined by the claimsappended hereto.

The embodiment(s) described, and references in the specification to “oneembodiment,” “an embodiment,” “some embodiments,” “other embodiments,”“an example embodiment,” “for example,” “exemplary,” etc., indicate thatthe embodiment(s) described may include a particular feature, structure,or characteristic, but every embodiment may not necessarily include theparticular feature, structure, or characteristic. Moreover, such phrasesare not necessarily referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with an embodiment, it is understood that it is within theknowledge of one skilled in the art to effect such feature, structure,or characteristic in connection with other embodiments whether or notexplicitly described.

Before describing such embodiments in more detail, however, it isinstructive to present an example environment in which embodiments ofthe present invention may be implemented.

Exemplary Reflective Lithographic System

FIG. 1 schematically shows a lithographic apparatus 100 including asource collector module SO according to an embodiment. The apparatuscomprises: an illumination system (illuminator) IL configured tocondition a radiation beam B (e.g., EUV radiation); a support structure(e.g., a mask table) MT constructed to support a patterning device(e.g., a mask or a reticle) MA and connected to a first positioner PMconfigured to accurately position the patterning device; a substratetable (e.g., a wafer table) WT constructed to hold a substrate (e.g., aresist-coated wafer) W and connected to a second positioner PWconfigured to accurately position the substrate; and a projection system(e.g., a reflective projection system) PS configured to project apattern imparted to the radiation beam B by patterning device MA onto atarget portion C (e.g., comprising one or more dies) of the substrate W.

The illumination system may include various types of optical components,such as refractive, reflective, magnetic, electromagnetic, electrostaticor other types of optical components, or any combination thereof, fordirecting, shaping, or controlling radiation.

The support structure MT holds the patterning device MA in a manner thatdepends on the orientation of the patterning device, the design of thelithographic apparatus, and other conditions, such as for examplewhether or not the patterning device is held in a vacuum environment.The support structure can use mechanical, vacuum, electrostatic or otherclamping techniques to hold the patterning device. The support structuremay be a frame or a table, for example, which may be fixed or movable asrequired. The support structure may ensure that the patterning device isat a desired position, for example with respect to the projectionsystem.

The term “patterning device” should be broadly interpreted as referringto any device that can be used to impart a radiation beam with a patternin its cross-section such as to create a pattern in a target portion ofthe substrate. The pattern imparted to the radiation beam may correspondto a particular functional layer in a device being created in the targetportion, such as an integrated circuit.

The patterning device may be reflective (as in lithographic apparatus100 of FIG. 1) or transmissive. Examples of patterning devices includemasks, programmable mirror arrays, and programmable LCD panels. Masksare well known in lithography, and include mask types such as binary,alternating phase-shift, and attenuated phase-shift, as well as varioushybrid mask types. An example of a programmable mirror array employs amatrix arrangement of small mirrors, each of which can be individuallytilted so as to reflect an incoming radiation beam in differentdirections. The tilted mirrors impart a pattern in a radiation beamwhich is reflected by the mirror matrix.

The projection system, like the illumination system, may include varioustypes of optical components, such as refractive, reflective, magnetic,electromagnetic, electrostatic or other types of optical components, orany combination thereof, as appropriate for the exposure radiation beingused, or for other factors such as the use of a vacuum. It may bedesired to use a vacuum for EUV radiation since other gases may absorbtoo much radiation. A vacuum environment may therefore be provided tothe whole beam path with the aid of a vacuum wall and vacuum pumps.

As here depicted, the lithographic apparatus is of a reflective type(e.g., employing a reflective mask).

The lithographic apparatus may be of a type having two (dual stage) ormore substrate tables (and/or two or more mask tables). In such“multiple stage” machines the additional tables may be used in parallel,or preparatory steps may be carried out on one or more tables while oneor more other tables are being used for exposure.

Referring to FIG. 1, the illuminator IL receives an extreme ultra violetradiation beam from the source collector apparatus SO. Methods toproduce EUV radiation include, but are not necessarily limited to,converting a material into a plasma state that has at least one element,e.g., xenon, lithium or tin, with one or more emission lines in the EUVrange. In one such method, often termed laser produced plasma (“LPP”)the required plasma can be produced by irradiating a fuel, such as adroplet, stream or cluster of material having the required line-emittingelement, with a laser beam. The source collector apparatus SO may bepart of a EUV radiation system including a laser, not shown in FIG. 1,for providing the laser beam exciting the fuel. The resulting plasmaemits output radiation, e.g., EUV radiation, which is collected using aradiation collector, disposed in the source collector apparatus. Thelaser and the source collector apparatus may be separate entities, forexample when a CO₂ laser is used to provide the laser beam for fuelexcitation.

In such cases, the laser is not considered to form part of thelithographic apparatus and the laser beam is passed from the laser tothe source collector apparatus with the aid of a beam delivery systemcomprising, for example, suitable directing mirrors and/or a beamexpander.

In an alternative method, often termed discharge produced plasma (“DPP”)the EUV emitting plasma is produced by using an electrical discharge tovaporize a fuel. The fuel may be an element such as xenon, lithium ortin which has one or more emission lines in the EUV range. Theelectrical discharge may be generated by a power supply which may formpart of the source collector apparatus or may be a separate entity thatis connected via an electrical connection to the source collectorapparatus.

The illuminator IL may comprise an adjuster for adjusting the angularintensity distribution of the radiation beam. Generally, at least theouter and/or inner radial extent (commonly referred to as σ-outer andσ-inner, respectively) of the intensity distribution in a pupil plane ofthe illuminator can be adjusted. In addition, the illuminator IL maycomprise various other components, such as facetted field and pupilmirror devices. The illuminator may be used to condition the radiationbeam, to have a desired uniformity and intensity distribution in itscross-section.

The radiation beam B is incident on the patterning device (e.g., mask)MA, which is held on the support structure (e.g., mask table) MT, and ispatterned by the patterning device. After being reflected from thepatterning device (e.g., mask) MA, the radiation beam B passes throughthe projection system PS, which focuses the beam onto a target portion Cof the substrate W. With the aid of the second positioner PW andposition sensor PS2 (e.g., an interferometric device, linear encoder orcapacitive sensor), the substrate table WT can be moved accurately,e.g., so as to position different target portions C in the path of theradiation beam B. Similarly, the first positioner PM and anotherposition sensor PS1 can be used to accurately position the patterningdevice (e.g., mask) MA with respect to the path of the radiation beam B.Patterning device (e.g., mask) MA and substrate W may be aligned usingmask alignment marks M1, M2 and substrate alignment marks P1, P2.

The depicted apparatus could be used in at least one of the followingmodes:

In step mode, the support structure (e.g., mask table) MT and thesubstrate table WT are kept essentially stationary, while an entirepattern imparted to the radiation beam is projected onto a targetportion C at one time (i.e., a single static exposure). The substratetable WT is then shifted in the X and/or Y direction so that a differenttarget portion C can be exposed.

In scan mode, the support structure (e.g., mask table) MT and thesubstrate table WT are scanned synchronously while a pattern imparted tothe radiation beam is projected onto a target portion C (i.e., a singledynamic exposure). The velocity and direction of the substrate table WTrelative to the support structure (e.g., mask table) MT may bedetermined by the (de-) magnification and image reversal characteristicsof the projection system PS.

In another mode, the support structure (e.g., mask table) MT is keptessentially stationary holding a programmable patterning device, and thesubstrate table WT is moved or scanned while a pattern imparted to theradiation beam is projected onto a target portion C. In this mode,generally a pulsed radiation source is employed and the programmablepatterning device is updated as required after each movement of thesubstrate table WT or in between successive radiation pulses during ascan. This mode of operation can be readily applied to masklesslithography that utilizes programmable patterning device, such as aprogrammable mirror array of a type as referred to above.

Combinations and/or variations on the above described modes of use orentirely different modes of use may also be employed.

FIG. 2 shows the lithographic apparatus 100 in more detail, includingthe source collector apparatus SO, the illumination system IL, and theprojection system PS. The source collector apparatus SO is constructedand arranged such that a vacuum environment can be maintained in anenclosing structure 220 of the source collector apparatus SO. A EUVradiation emitting plasma 210 may be formed by a discharge producedplasma source. EUV radiation may be produced by a gas or vapor, forexample Xe gas, Li vapor or Sn vapor in which the very hot plasma 210 iscreated to emit radiation in the EUV range of the electromagneticspectrum. The very hot plasma 210 is created by, for example, anelectrical discharge causing an at least partially ionized plasma.Partial pressures of, for example, 10 Pa of Xe, Li, Sn vapor or anyother suitable gas or vapor may be required for efficient generation ofthe radiation. In an embodiment, a plasma of excited tin (Sn) isprovided to produce EUV radiation.

The radiation emitted by the hot plasma 210 is passed from a sourcechamber 211 into a collector chamber 212 via an optional gas barrier orcontaminant trap 230 (in some cases also referred to as contaminantbarrier or foil trap) which is positioned in or behind an opening insource chamber 211. The contaminant trap 230 may include a channelstructure. Contamination trap 230 may also include a gas barrier or acombination of a gas barrier and a channel structure. The contaminanttrap or contaminant barrier 230 further indicated herein at leastincludes a channel structure, as known in the art.

The collector chamber 212 may include a radiation collector CO which maybe a so-called grazing incidence collector. Radiation collector CO hasan upstream radiation collector side 251 and a downstream radiationcollector side 252. Radiation that traverses collector CO can bereflected off a grating spectral filter 240 to be focused in a virtualsource point IF. The virtual source point IF is commonly referred to asthe intermediate focus, and the source collector apparatus is arrangedsuch that the intermediate focus IF is located at or near an opening 219in the enclosing structure 220. The virtual source point IF is an imageof the radiation emitting plasma 210. Grating spectral filter 240 isused in particular for suppressing infra-red (IR) radiation.

Subsequently the radiation traverses the illumination system IL, whichmay include a facetted field mirror device 222 and a facetted pupilmirror device 224 arranged to provide a desired angular distribution ofthe radiation beam 221, at the patterning device MA, as well as adesired uniformity of radiation intensity at the patterning device MA.Upon reflection of the beam of radiation 221 at the patterning deviceMA, held by the support structure MT, a patterned beam 226 is formed andthe patterned beam 226 is imaged by the projection system PS viareflective elements 228, 230 onto a substrate W held by the wafer stageor substrate table WT.

More elements than shown may generally be present in illumination opticsunit IL and projection system PS. The grating spectral filter 240 mayoptionally be present, depending upon the type of lithographicapparatus. Further, there may be more mirrors present than those shownin the figures, for example there may be 1-6 additional reflectiveelements present in the projection system PS than shown in FIG. 2.

Collector optic CO, as illustrated in FIG. 2, is depicted as a nestedcollector with grazing incidence reflectors 253, 254 and 255, just as anexample of a collector (or collector mirror). The grazing incidencereflectors 253, 254 and 255 are disposed axially symmetric around anoptical axis O and a collector optic CO of this type is preferably usedin combination with a discharge produced plasma source, often called aDPP source.

Exemplary Embodiments of an Object Support

In some embodiments, a support of a lithographic apparatus is configuredto hold an object and control the temperature of the object. The supportcan be a substrate table WT configured to hold substrate W or a supportstructure MT configured to hold patterning device MA as described abovein FIGS. 1 and 2. The object can be, for example, a patterning devicesuch as a mask or reticle as described above, or the object can be, forexample, a substrate such as a wafer as described above. In someembodiments in which the object is a patterning device, patterningdevice imparts a pattern onto a beam of radiation incident on a surfaceof patterning device. When the object is clamped to the clamp, a surfaceof the object receives a radiation beam. When the object is exposed withan incident radiation beam, the object can absorb power from theradiation beam and heat up. When the object is heated, portions of theobject can expand and deform. In some embodiments, to prevent or reducedeformation of object, the support can be configured to condition theobject to be held at substantially room temperature (for example, about22° C.) or any other defined operating temperature, according to variousembodiments. The clamp is configured to act as a heat sink, and theclamp can be configured to be maintained at a temperature lower than thetarget average temperature of the object to accomplish this temperaturecontrol of the object. In some embodiments, the clamp is maintained at atemperature lower than the target temperature of object by passing afluid conditioned to a target temperature through at least one channeldefined by clamp. But over time, the cooling power of fluid passingthrough the at least one channel will also cool the chuck, causingdeformation of the chuck which in turn leads to deformation of the clampand the object. In an embodiment in which the object is a patterningdevice having a reflective surface, portions of the reflective surfacecan be deformed, causing unwanted image distortion at the substratewafer. Additionally, deformation of the object can cause slip betweenthe chuck and the object. Moreover, chuck deformations, by itself, canalso lead to changes in the chuck metrology leading to chuck positioningerrors and, consequently, image overlay errors at the substrate wafer.

To eliminate or reduce this deformation of the clamped object as well aschuck positioning errors due to deformation of the chuck, a supportconfigured to hold an object of a lithographic apparatus can include aclamp with both (1) at least one channel configured to pass a fluid tocondition a chuck at target temperature and (2) at least one separatechannel configured to pass a fluid to condition the object at targettemperatures in an embodiment. FIG. 3 shows a cross-sectional diagram ofa portion of a lithographic apparatus according to one such embodiment.

FIG. 3 illustrates a support 400 configured to hold and control thetemperature of an object 402 and control the temperature of object 402and of chuck 404. Support 400 can be a substrate table WT configured tohold a substrate W or can be a support structure MT configured to hold apatterning device MA as described above in FIGS. 1 and 2. Accordingly,object 402 can be, for example, patterning device MA such as a mask orreticle as described above, or object 402 can be, for example, asubstrate W such as a wafer as described above. In some embodiments inwhich object 402 is a patterning device, patterning device 402 imparts apattern onto an incident beam of radiation 403.

In some embodiments, support 400 includes a chuck 404 and a clamp 406coupled to chuck 404. For example, clamp 406 can be bonded to chuck 404.Clamp 406 is configured to selectively couple object 402 to chuck 404such that object 402 moves along with chuck 404. In some embodiments,clamp 406 is an electrostatic clamp. For example, clamp 406 can beconfigured to generate an electrostatic field to hold object 402 inplace. In such electrostatic embodiments, clamp 406 can includeelectrodes (not shown) that generate this electrostatic field.

Clamp 406 defines a mounting surface 416 configured to receive object402 (e.g., a substrate W or a patterning device MA). In someembodiments, mounting surface 416 is planar as shown in FIG. 3. In otherembodiments (not shown), mounting surface 416 is non-planar. Forexample, mounting surface 416 can have protruding burls configured tocontact object 402 during clamping operation of clamp 406.

In some embodiments, clamp 406 is made of a single layer as shown inFIG. 3. In other embodiments (not shown), clamp 406 can be made of aplurality of layers.

In some embodiments, clamp 406 is composed of one or more dielectricmaterials configured to support an electrostatic field during operationof clamp 406 as described above. In some embodiments, the dielectricmaterials can have ultra-low coefficients of thermal expansion that arezero or substantially zero. Materials having ultra-low coefficients ofthermal expansion include, but not limited to, ultra-low expansionsilicon-based materials (e.g., ULE® glass manufactured by Corning),glass materials, ceramic materials, silicon-based glass ceramicmaterials (e.g., ZERODUR® glass ceramic manufactured by SCHOTT), or acombination thereof. Using materials that have ultra-low coefficients ofthermal expansion can help reduce thermal stress in clamp 406 which maybe transferred to object 402 during clamping operation.

In some embodiments, clamp 406 is composed of one or more materialshaving ultra-low coefficients of thermal expansion that vary as afunction of temperature. FIG. 5 charts the coefficient of thermalexpansion of one such material as a function of temperature according toan embodiment. Referencing FIG. 5, the temperature at which thecoefficient of thermal expansion is about zero is called thezero-crossing temperature T_(zc). If this function is substantiallylinear as shown in FIG. 5, the internal forces generated within clamp406 will be a second order polynomial function of temperature as shownin FIG. 6, which illustrates an exemplary diagram of internal thermalforces F of clamp 406 due to expansion of the material as a function oftemperature. As shown in FIG. 6, if the temperature of the material isabout equal to the zero-crossing temperature T_(zc) of the material, thegenerated internal thermal forces within clamp 406 are about zero. F=0is defined with respect to the undeformed state (desired or calibratedshape) of the respective component the material composes, for example,object 402 or clamp 406. In the embodiment of FIG. 6, the temperature ofthe component, for example, object 402 or clamp 406, at the undeformedstate is about equal to the zero-crossing temperature of the materialcomposing the component. As the temperature of the material moves awayfrom the zero-crossing temperature T_(zc), the generated internal forcesof clamp 406 increase in a quadratic fashion symmetric about thevertical axis crossing through the zero-crossing temperature T_(zc).

In some embodiments, clamp 406 is composed of a material that has acoefficient of thermal expansion that varies as a function oftemperature and that has a zero-crossing temperature deviatingsubstantially from the undeformed temperature of clamp 406 (for example,room temperature or about 22° C.) or any other target operatingtemperature of the lithographic apparatus. In other embodiments, clamp406 is composed of a material that has a coefficient of thermalexpansion that varies as a function of temperature and that has azero-crossing temperature less than or more than about room temperature(for example, less than or more than about 22° C.). In some embodiments,clamp 406 is composed of a material that has a coefficient of thermalexpansion that varies as a function of temperature and that has azero-crossing temperature that is less than a zero-crossing temperatureof the material composing object 402 (which can also be composed of amaterial that has a coefficient of thermal expansion that varies as afunction of temperature in some embodiments).

Turning back to FIG. 3, clamp 406 has a thickness (i.e., in a directionperpendicular to mounting surface 416) in a range from about 4 mm toabout 12 mm in some embodiments. For example, in some embodiments, clamp406 has a thickness of about 8 mm. In some embodiment, clamp 406 has athickness greater than a thickness of object 402.

In some embodiments, object 402 is composed of one or more materialshaving ultra-low coefficients of thermal expansion that are zero orsubstantially zero. Materials having ultra-low coefficients of thermalexpansion include, but not limited to, ultra-low expansion silicon-basedmaterials (e.g., ULE® glass manufactured by Corning), glass materials,ceramic materials, silicon-based glass ceramic materials (e.g., ZERODUR®glass ceramic manufactured by SCHOTT), or a combination thereof.

In some embodiments, object 402 is composed of one or more materialshaving ultra-low coefficients of thermal expansion that vary as afunction of temperature. Again, FIG. 5 charts the coefficient of thermalexpansion of one such material as a function of temperature according toan embodiment. Referencing FIG. 5, the temperature at which thecoefficient of thermal expansion is about zero is called thezero-crossing temperature T_(zc). If this function is substantiallylinear as shown in FIG. 5, the internal thermal forces generated withinobject 402 will vary substantially as a second order polynomial functionof temperature as shown in FIG. 6. In some embodiments, object 402 iscomposed of a material that has a coefficient of thermal expansion thatvaries as a function of temperature and that has a zero-crossingtemperature equal to about room temperature (for example, about 22° C.)or any other target operating temperature of the lithographic apparatus.In other embodiments, object 402 is composed of a material that has acoefficient of thermal expansion that varies as a function oftemperature and that has a zero-crossing temperature less than or morethan about room temperature (for example, less than or more than about22° C.). In some embodiments, object 402 is composed of a material thathas a coefficient of thermal expansion that varies as a function oftemperature and that has a zero-crossing temperature that is more than azero-crossing temperature of the material composing clamp 406 (which canalso be composed of a material that has a coefficient of thermalexpansion that varies as a function of temperature in some embodimentsas described above). Referencing FIG. 6 in which the temperature ofobject 402 at the undeformed state is about equal to the zero-crossingtemperature of the material composing object 402, if the temperature ofa portion of object 402 is about equal to the zero-crossing temperatureT_(zc), the generated internal forces within object 402 at that point isabout zero. As the temperature of a portion of object 402 moves awayfrom the zero-crossing temperature T_(zc) of the material, the generatedinternal forces of object 402 increase in a quadratic fashion symmetricabout the vertical axis crossing the zero-crossing temperature T_(zc).

In other embodiments, object 402 is composed of a material havingultra-low coefficients of thermal expansion that vary as a function oftemperature, and the zero-crossing temperature of the material isgreater than the temperature of object 402 at the undeformed state(desired or calibrated shape). For example, the zero-crossingtemperature of the material composing object 402 can be about 30° C.,and the temperature of object 402 at the undeformed state can be about20° C. FIG. 14 illustrates the internal forces generated within object402 due to expansion of the material as a function of temperatureaccording to one such embodiment.

In some embodiments, object 402 is composed of one or more materialshaving ultra-low coefficients of thermal expansion that vary as afunction of temperature, and clamp 406 is composed of one or morematerials having ultra-low coefficients of thermal expansion that varyas a function of temperature. In some of these embodiments, thezero-crossing temperature of the one or more materials composing object402 is higher than the zero-crossing temperature of the one or morematerials composing clamp 406. For example, in some embodiments, thezero-crossing temperature of the material(s) composing object 402 isabout 22° C., and the zero-crossing temperature of the material(s)composing clamp 406 is about 8° C. In other embodiments, thezero-crossing temperature of the one or more materials composing object402 is lower than the zero-crossing temperature of the one or morematerials composing clamp 406. In yet other embodiments, thezero-crossing temperature of the one or more materials composing object402 is about equal to the zero-crossing temperature of the one or morematerials composing clamp 406.

When object 402 is clamped to clamp 406, a surface 412 of object 402 isadjacent mounting surface 416 of clamp 406, and a surface 414 opposingsurface 412 of object 402 faces away from clamp 406 and chuck 404.Surface 414 of object 402 receives radiation beam 403. When object 402is exposed to incident radiation beam 403, object 402 can absorb powerfrom radiation beam 403 and heat up. For example, radiation beam 403 candeliver a target wattage such that the absorption power at object 402can be, for example, 3-500 Watts (such as 28 Watts or 80 Watts). In someembodiments, radiation beam 403 is from projection system PS describedabove and/or other systems of lithographic apparatus 100 during theiroperation.

To prevent or reduce the deformation of object 402 due to the absorptionof heat from radiation beam 403, support 400 can be configured tocondition object 402 to be held at substantially room temperature (forexample, about 22° C.) or any other defined operating temperature, andconfigured to condition chuck 404 to be held at substantially roomtemperature (for example, about 22° C.) or any other defined operatingtemperature, according to various embodiments. In some embodiments,clamp 406 is configured to act as a heat sink for object 402. Forexample, a portion of clamp 406 that receives object 402 can beconfigured to be maintained at a temperature lower than the targetaverage temperature of object 402 (for example, less than about 22° C.)to accomplish this temperature control of object 402. For example, ifthe target average temperature of object 402 is about 22° C. (forexample, about the zero-crossing temperature of the material composingobject 402), a portion of clamp 406 that receives object 402, forexample, the portion of clamp 406 having mounting surface 416, can bemaintained at a temperature less than about 22° C., for example, about−8° C. Through contact between clamp 406 and object 402 (for example,contact between mounting surface 416 of clamp 406 and surface 412 ofobject 402), heat can be transferred from object 402 to clamp 406.

In some embodiments, a portion of clamp 406 that receives object 402 ismaintained at a temperature lower than the target average temperature ofobject 402 by passing a fluid through at least one channel 408 definedby clamp 406, which conditions the temperature of the receiving portionof clamp 406. As shown in FIG. 3, clamp 406 can define a plurality ofchannels 408 in some embodiments. In other embodiments (not shown),clamp 406 defines a single channel 408. Channels 408 are configured tocirculate the conditioned fluid through clamp 406. In some embodiments,passing fluid through channels 408 maintains the portion of clamp 406that receives object 402 at a substantially constant temperature lowerthan the target average temperature of object 402. Thereby, clamp 406continuously removes heat from object 402. Channels 408 can beconfigured to run parallel to mounting surface 416 of clamp 406 in someembodiments. In some embodiments, the fluid (i.e., a liquid or gas) iswater, air, an alcohol, a glycol, a phase change coolant (e.g., Freons,carbon dioxide), or a combination thereof.

In some embodiments, support 400 includes a fluid conditioning device410 that is coupled to channels 408 to condition a characteristic, forexample, temperature, of the fluid before entering clamp 406 throughchannels 408. In some embodiments, fluid conditioning device 410comprises one or more thermoelectric cooling devices such as a Peltiercooler or any other suitable thermoelectric cooling device. In otherembodiments, fluid conditioning device 410 comprises one or more heatexchangers such as a shell and tube heat exchanger, a plate heatexchanger, or any other suitable heat exchanger. In some embodiments,fluid conditioning device 410 comprises a combination of one or morethermoelectric cooling devices and one or more heat exchangers.

In some embodiments, the fluid passing through channels 408 isrecirculated. For example, the fluid exits channels 408 and clamp 406and is then routed back to fluid conditioning device 410 via one or moreducts before entering clamp 406 via channels 408. In other embodiments,the fluid passing through channels 408 is not-recirculated andoriginates from a fluid source upstream from fluid conditioning device410.

In some embodiments, the cooling power of fluid conditioning device 410is adjustable, for example, based on a control signal received from acontroller 413. In such embodiments, the temperature of the fluidentering channels 408 within clamp 406 can be selectively adjusted.Selectively adjusting the temperature of the fluid entering channels 408changes the temperature of surface 416 of clamp 406 and, consequently,changes the temperature of surface 412 of object 402. For example, FIG.4 illustrates the temperature adjustable control of the fluid enteringchannels 408 according to an embodiment. For example, collectivelyreferencing FIGS. 3 and 4, controller 413 can send a control signal tofluid conditioning device 410. At a first time t₁, fluid conditioningdevice 410 conditions the temperature T₁ of fluid entering channels 408to have a first temperature. Then at a subsequent time t₂, controller413 can send a control signal to fluid conditioning device 410 such thatat time t₂, fluid conditioning device 410 conditions the temperature T₂of fluid entering channels 408 to have a second temperature, which isdifferent than the first temperature. In some embodiments, the secondtemperature of fluid entering channels 408 is less than the firsttemperature of fluid entering channels 408 as shown in FIG. 4. Forexample, the first temperature of fluid entering channels 408 at time t₁can be about room temperature (for example, about 22° C.), and thesecond temperature of fluid entering channels 408 at time t₂ can be, forexample, about −8° C. In some embodiments, the first temperature offluid entering channels 408 at time t₁ is in a range from about 17° C.to about 27° C., for example, about 22° C. In some embodiments, thesecond temperature of fluid entering channels 408 at time t₂ is in arange from about −15° C. to about 15° C., for example, about −8° C. or2° C.

In some embodiments, the second temperature of fluid entering channels408 at time t₂ is less than a target average temperature (for example,about the zero-crossing temperature of the material composing object 402or about 22° C.) of object 402 when object 402 device is being exposedwith radiation beam 403.

In some embodiments (not shown in FIG. 4), the second temperature offluid entering channels 408 at time t₂ is more than the firsttemperature of fluid entering channels 408 at time t₁.

In some embodiments, time t₂ at which point the temperature of fluidentering channels 408 is adjusted from the first temperature to thesecond temperature is switched coincides with the time at which object402 is subject to a heating power from being exposed with radiation beam403 as shown in FIG. 4. In other embodiments (not shown in FIG. 4), timet₂ does not coincide with the time at which object 402 is subject to aheating power from being exposed with radiation beam 403 as shown inFIG. 4.

In some embodiments, the second temperature of fluid entering channels408 of clamp 406 at time t₂ is such that clamp 406 conditions object 402to have an average temperature that is about equal to the zero-crossingtemperature of the material composing object 402. For example, if thezero-crossing temperature of the material composing object 402 is about22° C., the second temperature of fluid entering channels 408 at time t₂is such clamp 406 conditions object 402 to have an average temperatureof about to 22° C.—the zero-crossing temperature of the materialcomposing object 402.

In some embodiments in which object 402 is conditioned to have anaverage temperature that is equal to about the zero-crossing temperatureof the material composing object 402, the sum of the internal bendingmoments due to the internal thermal forces is about equal to zero (forexample, as shown in the embodiments in both FIG. 8 and FIG. 14). And inaddition to the sum of the internal bending moments being about equal tozero, the sum of the internal thermal forces can be about equal to zeroin some embodiments (for example, when the zero-crossing temperature ofthe material composing object 402 is greater than the temperature ofobject 402 at the undeformed state as shown in FIG. 14). In suchembodiments (i.e., embodiments in which the sum of internal moments isabout equal to zero and/or the sum of internal thermal forces is aboutequal to zero), the deformation of object 402 can be reduced (which canlead to smaller and better correctable deformation shapes). Oneadvantage of conditioning object 402 to have an average temperature thatis equal to about the zero-crossing temperature of the materialcomposing object 402 is that the sensitivity for spatial variation ofthe exposure heat load can be reduced. Another advantage of conditioningobject 402 to have an average temperature that is equal to about thezero-crossing temperature of the material composing object 402 is thatthe sensitivity for spatial zero-crossing variation of the materialcomposing object 402 can also be reduced.

In other embodiments, the second temperature of fluid entering channels408 at time t₂ is such that clamp 406 conditions object 402 to have anaverage temperature that is less than or more than the zero-crossingtemperature of the material composing object 402.

In some embodiments, the transition from the first temperature of thefluid entering channels 408 at time t₁ to the second temperature offluid entering channels 408 at time t₂ is stepped as shown in FIG. 4. Inother embodiments, the transition is not stepped.

To prevent or reduce the deformation of chuck 404 due to the coolingpower of fluid passing through channels 408 of clamp 406, support 400can be configured to condition a portion of clamp 406 between channels408 and chuck 404. for example, a portion of clamp 406 including surface418 of clamp 406 can be maintained at a temperature higher than thetemperature of the fluid passing through channels 408. In someembodiments, a portion of clamp 406 between channels 408 and chuck 404can be maintained at a higher temperature by passing a fluid at atemperature higher than the temperature of the fluid passing throughchannels 408 through at least one channel 422 between channel(s) 408 andchuck 404 and that is separate from channel(s) 408. As shown in FIG. 3,clamp 406 can define a plurality of channels 422 in some embodiments. Inother embodiments (not shown), clamp 406 defines a single channel 422.Channels 422 are configured to circulate the conditioned fluid throughclamp 406. Passing fluid through channels 422 maintains the portion ofclamp 406 between channels 408 and chuck 404 at a substantially constanttemperature higher than the temperature of the fluid passing throughchannels 408. Thereby, clamp 406 continuously conditions chuck 404 tohave a temperature, for example, about 22° C., that prevents or reducesdeformation of chuck 404.

Channels 422 can be configured to run parallel to mounting surface 416of clamp 406 in some embodiments. In some embodiments, the fluid (i.e.,a liquid or gas) passing through channels 422 is water, air, an alcohol,a glycol, a phase change coolant (e.g., Freons, carbon dioxide), or acombination thereof. As shown in FIG. 3, channels 422 are between chuck404 and channels 408, and channels 422 are separate from channels 408 insome embodiments.

In some embodiments, support 400 includes a fluid conditioning device411 coupled to channels 422 to condition a characteristic, for example,temperature, of the fluid passing through channels 422 before enteringclamp 406. In some embodiments, fluid conditioning device 411 comprisesone or more thermoelectric cooling devices such as a Peltier cooler orany other thermoelectric cooling device. In other embodiments, fluidconditioning device 411 comprises one or more heat exchangers such as ashell and tube heat exchanger, a plate heat exchanger, or any other heatexchanger. In some embodiments, fluid conditioning device 411 comprisesa combination of one or more of thermoelectric cooling device and one ormore heat exchangers.

In some embodiments, the fluid passing through channels 422 isrecirculated. For example, the fluid exits channels 422 and clamp 406and is then routed back to fluid conditioning device 411 via one or moreducts before entering clamp 406 via channels 422. In other embodiments,the fluid passing through channels 422 is not-recirculated andoriginates from a fluid source upstream from fluid conditioning device411.

In some embodiments, the cooling power of fluid conditioning device 411is based on a control signal received from controller 413. In someembodiments, the temperature of the fluid entering channels 422 withinclamp 406 can be maintained at a constant temperature. For example, asshown in FIG. 4, controller 413 can send a control signal to fluidconditioning device 411 such that at a first time t₁ and a subsequentsecond time t₂, fluid conditioning device 411 conditions the fluidentering channels 422 to have a substantially constant temperature T₂.In some embodiments, the temperature of fluid entering channels 422 isabout room temperature (for example, about 22° C.). In some embodiments,the first temperature of fluid entering channels 422 is in a range fromabout 17° C. to about 27° C., for example, about 22° C. In someembodiments, the temperature of fluid entering channels 422 is greaterthan the temperature of fluid entering channels 408 at time t₂ as shownin FIG. 4.

In other embodiments, the temperature conditioning power of fluidconditioning device 411 is adjustable, for example, based on a controlsignal received from controller 413. In such embodiments, thetemperature of the fluid entering channels 422 within clamp 406 can beselectively adjusted. Selectively adjusting the temperature of the fluidentering channels 422 changes the temperature conditioning power ofclamp 406 on chuck 404.

FIG. 7 illustrates the temperature of object 402 and clamp 406 havingchannels 408 and 422, according to an embodiment, at various times T1-T8after (1) object 402 is exposed with radiation beam 403, and (2) thetemperature of fluid entering channels 408 is adjusted from a firsttemperature to a lower second temperature. In this embodiment, thecooling power on object 402 generated by passing fluid through channels408 at the second temperature is about equal to a heating power appliedto object 402 during exposure with radiation 403, and the averagetemperature of object 402 remains over time about equal to thezero-crossing temperature of the material composing object 402. Forexample, when object 402 is exposed with 80 W from radiation beam 403,the temperature of fluid entering channels 408 is adjusted from about22° C. to about −8° C. such that the cooling power on surface 412, overtime, is about equal to 80 W heating power absorbed by object 402 duringexposure with radiation 403. Accordingly, the average temperature ofobject 402 remains, over time, equal to about to room temperature, forexample, about 22° C., which is also about the zero-crossing temperatureof the material composing object 402 in some embodiments.

In FIG. 7, the horizontal axis corresponds to a position on object 402or clamp 406 in a direction substantially perpendicular to mountingsurface 416 of clamp 406 and surface 414 of object 402. For example, thedashed line at the right end of the horizontal axis corresponds tosurface 414 of object that receives radiation beam 403. The dashed lineat the left end of the horizontal axis corresponds to surface 418 ofclamp 406 that is adjacent chuck 404. The intermediate dashed line 416,412 to the left of dashed lane 414 corresponds to the interface betweenmounting surface 416 of clamp 406 and surface 412 of object 402, whichis adjacent to mounting surface 416. The dashed line 408 to the left ofdashed line 416, 412 corresponds to the location of channels 408 ofclamp 406, and the dashed line to the left of dashed line 408corresponds to the location of channels 422. Notably, the discontinuityof the temperatures at the interface 416, 412 between mounting surface416 of clamp 406 and surface 412 of object 402 is due to the thermalresistance of a back-fill pressure between clamp 406 and object 402.

As shown in FIG. 7, after surface 414 of object 402 is exposed with a 80W radiation beam 403 and after the temperature of fluid enteringchannels 408 is adjusted to about −8° C., the temperature of a portionof object 402 including surface 414 increases from about 22° C. fromtime T1 to time T8, and the temperature of a portion of object 402including surface 412 decreases from time T1 to time T8. Object 402 hasa thickness in the range of about 4 mm to about 8 mm and comprises amaterial having ultra-low coefficient of thermal expansion that variesas a function of temperature and has a zero-crossing temperature ofabout 22° C. In some embodiments, clamp 406 has a thickness in the rangeof about 6 mm to about 10 mm, for example, 8 mm, and comprises amaterial having ultra-low coefficient of thermal expansion that variesas a function of temperature and has a zero-crossing temperature ofabout 22° C. (Although in some embodiments, clamp 406 comprises amaterial having ultra-low coefficient of thermal expansion that has azero-crossing temperature, for example, about 8° C., less than thezero-crossing temperature of the material composing object 402.) In someembodiments, time T8 is about 200 seconds after surface 414 of object402 is exposed with radiation beam 403 and after the temperature offluid entering channels 408 is adjusted to the lower temperature, forexample, about −8° C.

As shown in FIG. 7, the average temperature of object 402 at times T1-T8is about 22° C., which is about the zero-crossing temperature of thematerial composing object 402 in some embodiments. The portion of object402 including surface 414 of object 402 is hotter than about 22° C.(i.e., hotter than about the zero-crossing temperature of the materialcomposing object 402), and the portion of object 402 including surface412 of object 402 is colder than about 22° C. (i.e., colder than aboutthe zero-crossing temperature of the material composing object 402). Forexample, the temperature of object 402 at surface 414 can be about 38°C. when exposed with radiation 403 at time T8. The temperature of object402 decreases in the direction of clamp 406 until the temperature ofobject 402 at about the midpoint of object 402 is about 22° C. (i.e.,about the zero-crossing temperature of the material composing object402). From that point on object 402, the temperature of object 402continues to decrease in the direction of clamp 406 until thetemperature of object 402 is about 10° C. at surface 412 of object 402at time T8.

Due to the resulting cooling by clamp 406, the average temperature ofobject 402 remains (during substantially the entire transition from timeT1 to time T8 in some embodiments) at about the zero-crossingtemperature of the material composing object 402, for example, at about22° C. And in some embodiments as shown in FIG. 7, the differencebetween the average temperature of object 402 (about the zero-crossingtemperature of the material composing object 402) and the temperature ofobject 402 at surface 412 is about equal to the difference between theaverage temperature of object 402 (about the zero-crossing temperatureof the material composing object 402) and the temperature of object 402at surface 414 during the transition from time T1 to time T8. Thistemperature distribution can generate a substantially symmetric internalthermal force distribution about an axis substantially parallel tosurface 414 of object 402 due to expansion of object 402 as shown inFIG. 8. In FIG. 8, force F1 corresponds to the internal thermal forcegenerated at surface 414 of object 402 having a temperature of about 38°C., and force F2 corresponds to the internal thermal force generated inobject 402 at a point between surface 414 and the point in object 402having a temperature of about 22° C. (i.e., about the zero-crossingtemperature of the material composing object 402). Force F3 correspondsto the internal thermal force generated in object 402 at a point betweenthe point in object 402 having a temperature of about 22° C. and surface412 of object 402, and force F4 corresponds to the internal thermalforce generated at surface 412 of object 402. FIG. 9 schematicallydiagrams the distribution of forces F1-F4 on object 402.

As shown in FIG. 9, forces F1-F4 are substantially symmetrical about anaxis parallel with surface 414 of object 402 that intersects a point onobject 402 having a temperature equal to about the zero-crossingtemperature of the material composing object 402, for example, about 22°C. This substantially symmetric force distribution can help reduce theinternal bending moments applied to object 402 by internal thermalforces generated by expansion of object 402, which can help reducedeformation of object 402.

FIG. 14 illustrates another example of a symmetric internal thermalforce distribution about an axis substantially parallel to surface 414of object 402 due to expansion of object 402 that can be achieved fromthe resulting cooling by clamp 406. In this embodiment, object 402 iscomposed of a material having a zero-crossing temperature (for example,about 30° C. as shown in FIG. 14) that is greater than a temperature ofobject 402 at its undeformed state (for example, about 20° C. as shownin FIG. 14). In FIG. 14, force F1 corresponds to the internal thermalforce generated at surface 414 of object 402 having a temperature ofabout 45° C., and force F2 corresponds to the internal thermal forcegenerated at a midpoint of object 402 having a temperature of about 30°C. (i.e., about the zero-crossing temperature of the material composingobject 402). Force F3 corresponds to the internal thermal forcegenerated at surface 412 of object 402 having a temperature of about 15°C. In FIG. 14, the sum of the internal bending moments due to theinternal thermal forces equal to about zero due to the symmetricinternal thermal force distribution. Also, the sum of the internalthermal forces in a plane parallel to surface 414 of object 402 is aboutequal to zero. Reducing the sum of the internal bending moments due tointernal thermal forces or by reducing the sum of internal thermalforces can reduce deformation of object 402.

In embodiments in which object 402 is a patterning device, reducingdeformation of object 402 and chuck 404 by passing fluid throughchannels 408 and 422 can reduce overlay errors over a pattern exposed ona substrate. For example, FIG. 10 charts the raw overlay error of apattern exposed on a substrate as a function of the position on thesubstrate at various times T1-T8 after object 402 is exposed withradiation beam 403 using support 400, according to an embodiment. Inthis embodiment, clamp 406 and object 402 have a temperaturedistribution as shown in FIG. 7, clamp 406 comprises a material havingultra-low coefficient of thermal expansion that varies as a function oftemperature, and object 402 comprises a material having ultra-lowcoefficient of thermal expansion that varies as a function oftemperature. In in this embodiment, the material composing clamp 406 hasa zero-crossing temperature, for example, about 22° C., that is aboutequal to the zero-crossing temperature, for example, about 22° C., ofthe material composing object 402. In FIG. 10, times T1-T8 correspondwith times T1-T8 in FIG. 7. In some embodiments, T8 can be about 200seconds (for example, 214 seconds) as shown in FIG. 7, and the maximumraw overlay error along the substrate from times T1-T8 is about 0.5 nmas shown in FIG. 10.

FIG. 11 charts the raw overlay error of a pattern exposed on a substrateas a function of the position on the substrate at various times T1-T8after object 402 is exposed with radiation beam 403 using support 400,according to another embodiment. In this embodiment, clamp 406 andobject 402 have a temperature distribution as shown in FIG. 7, clamp 406comprises a material having ultra-low coefficient of thermal expansionthat varies as a function of temperature, and object 402 comprises amaterial having ultra-low coefficient of thermal expansion that variesas a function of temperature. In in this embodiment, the materialcomposing clamp 406 has a zero-crossing temperature, for example, about8° C., that is less than about the zero-crossing temperature, forexample, about 22° C., of the material composing object 402. In FIG. 11,times T1-T8 correspond with times T1-T8 in FIG. 7. In some embodiments,time T8 can be about 200 seconds (for example, 214 seconds) as shown inFIG. 7, and the maximum raw overlay error along the substrate from timesT1-T8 is about 0.1 nm as shown in FIG. 11. The reduction in raw overlayerror in this embodiment relative to the embodiment in FIG. 10 isattributable, at least in part, to internal thermal forces generated inclamp 406. When clamp 406 has a temperature distribution as shown inFIG. 7, the internal forces generated in clamp 406 will be in theopposite direction of internal thermal expansion forces F1-F4 (see FIG.9) generated in object 402. These internal compressive thermal forcesgenerated in clamp 406 can resist the internal expansion thermal forcesF1-F4 (see FIG. 9) generated in object 402, which can help reducedeformation of object 402 and, in turn, reduce the overlay error at thesubstrate.

In some embodiments, support 400 includes a pellicle 424 as shown inFIG. 12. For example, one side of pellicle 424 can be mounted to alateral end portion 426 of object 402 and the other side of pellicle 424can be mounted to the opposing lateral end portion 428 of object 402. Insome embodiments, support 400 includes a mount 430, for example, asilicon carbide or metal stud, coupled to surface 414 of object 402 atlateral end portion 426 on one end of mount 430 and coupled to pellicle424 on the other end of mount 430. Support 400 also includes a mount432, for example, a silicon carbide or metal stud, coupled to surface414 of object 402 at lateral end portion 428 on one end of mount 432 andcoupled to pellicle 424 on the other end of mount 432. Mounts 430 and432 can be adhered directly to surface 414 of object 402 in someembodiments. In some embodiments, lateral end portions 426 and 428correspond to portions of object 402 that are not included in the fieldof exposure and that are not aligned with interfaces between object 402and clamp 406 that are back filled.

In some embodiments, controller 413 controls the temperature of thefluid passing through channels 408 such that lateral end portions 426and 428 of object 402 are maintained at substantially room temperature(for example, about 22° C.). FIG. 13 illustrates the temperature ofsurface 414 of object 402 having channels 408 and 422 according to onesuch embodiment at various times T1-T6 after: (1) object 402 is exposedwith radiation beam 403; and (2) the temperature of fluid enteringchannels 408 is adjusted from a first temperature to a lower secondtemperature as described in the above embodiments. In some embodiments,time T6 is about 300 seconds or more after exposure with radiation beam403 starts. In this embodiment, the temperature of surface 414 of object402 at lateral end portions 426 and 428 is about room temperature, forexample, about 22° C. Accordingly, mounts 430 and 432 will also remainat about room temperature, for example, about 22° C. Maintaining mounts430 and 432 at about room temperature can help reduce expansion ofmounts 430 and 432 during exposure, which in turn can reduce localdeformations of object 402.

In some embodiments, the portion of clamp 406 adjacent chuck 404, forexample, the portion including channels 422, is thermally isolated fromthe portion of chuck 404 that includes channels 408 by forming voids inclamp 406 there between. FIG. 15 illustrates one such embodiment ofclamp 406. As shown in FIG. 15, clamp 406 includes a first layer 434, asecond layer 436, and a third layer 438. First layer 434 includes aplurality of burls 440 that define surface 416 that receives object 402.Second layer 436 defines channels 408, and third layer 438 includes aplurality of burls 442 that define a plurality of voids 444. Third layer438 is coupled to chuck 404 at surface 418 of clamp 406.

In some embodiments, first, second, and third layers 434, 436, and 438are optically coupled to each other by anodic or fusion bonding. Forexample, first and second layers 434 and 436 can be fusion bondedtogether at interface 448, and second and third layers 436 and 438 canbe fusion bonded together at interface 446. And third layer 438 can beoptically coupled to chuck 404 (not shown) at surface 418. Afterbonding, first, second, and third layers 434, 436, and 438 is monolithicin some embodiments.

In other embodiments, clamp 406 is a single layer defining voids 444,channels 408, and channels 422.

In some embodiments, a vacuum is formed in voids 444. In someembodiments, the vacuum occurs during operational use of thelithographic apparatus. In other embodiments, voids 444 are filled witha thermally insulating fluid, for example, air or any other insulatingfluid. In some embodiments, voids 444 reduce thermal conduction betweenthird layer 438 adjacent chuck 404 and second layer 436 that includeschannels 408 by a factor of 50-100 relative to a similar clamp withoutvoids 444. In some embodiments, this thermal insulation provided byvoids 444 allows first and second layers 434 and 436 to operate attemperatures substantially lower than room temperature or 22° C., forexample, at temperatures below 2° C., while third layer 438 maintains atemperature about equal to the temperature of chuck 404 at itsundeformed, manufactured state, for example, about room temperature or22° C. This configuration can reduce residual thermal errors in chuck404 while also improving chuck stability and manufacturing.

Voids 444 decrease the thermal coupling (i.e., thermally isolates)between the portion of clamp 406 including channels 408 (for example,first layer 434 or second layer 436) from the portion of clamp 406adjacent chuck 404 (for example, third layer 438). When clamp 406includes channels 422, the resulting thermal isolation allows for asmaller temperature difference between the fluids passing throughchannels 408 and 422 and/or a smaller distance between channels 408 and422, which can improve scale stability and chuck flatness.

In some embodiments, channels 422 can be omitted from clamp 406. Becausevoids 444 thermally isolate the portion of clamp 406 contacting chuck404 from the portion of clamp 406 that includes channels 408,conditioning of chuck 404 via fluid flow in channels 422 is renderedunnecessary.

In some embodiments, the surface area of burls 442 that interface secondlayer 436 is less than 50 percent the surface area of the surface ofsecond layer 436 facing third layer 438. In some embodiments, thesurface area of burls 442 that interface second layer 436 is less than10 percent the surface area of the surface of second layer 436 facingthird layer 438.

In some embodiments, each of layers 434, 436, and 438 is composed of oneor more materials having ultra-low coefficients of thermal expansionthat vary as a function of temperature. For example, the materialcomposing layers 434, 436, and 438 can be ultra-low expansionsilicon-based materials (e.g., ULE® glass manufactured by Corning),glass materials, ceramic materials, silicon-based glass ceramicmaterials (e.g., ZERODUR® glass ceramic manufactured by SCHOTT), or acombination thereof.

In some embodiments, instead of clamp 406 having voids 444 as shown inFIG. 15, chuck 404 can have voids 464 that thermally isolate chuck 404from clamp 406 as shown in FIG. 16. This configuration (i.e., voids 464in chuck 404 instead of clamp 406) can simplify the structure of clamp406. For example, forming voids 464 in chuck 404, instead of clamp 406,can reduce the number of layers forming clamp 406. In FIG. 15, clamp 406having voids 444 is formed of three layers, but in FIG. 16, clamp 406without voids 444 is formed of two layers.

As shown in FIG. 16, clamp 406 can be made of a plurality of layers. Forexample, clamp 406 can include a first layer 450 and a second layer 452.First layer 450 includes plurality of burls 440 that define surface 416that receives object 402. Second layer 452 defines channels 408 and iscoupled to chuck 404.

In other embodiments (not shown), first layer 450 defines channels 408.

In other embodiments (not shown), clamp 406 is formed of a single layeror of more than two layers.

Although burls 440 in FIG. 16 have a trapezoidal cross-sectional shape,burls 440 can have other suitable cross-sectional shapes, for example, arectangular, triangular, or hemispherical shape.

Again, clamp 406 can be an electrostatic clamp that generates anelectrostatic field to hold object 402 in place in some embodiments. Insuch electrostatic embodiments, one or more of layers 450 and 452 caninclude electrodes (not shown) that generate this electrostatic field.

As shown in FIG. 16, chuck 404 can be made of a plurality of layers. Forexample, chuck 404 can include a first layer 454 that defines surface420 coupled to second layer 452 of clamp 406, and a second layer 456coupled to first layer 454.

In other embodiments (not shown), first layer 454 can be omitted suchthat layer 456 defining voids 464 is coupled directly to clamp 406 (forexample, to layer 452 of clamp 406.) In other embodiments (not shown),more than one layer of chuck 404 can be positioned between layer 456defining voids 464 and clamp 406. In other embodiments, chuck 404 isformed of a single layer or of more than two layers (for example, three,four, or five layers). For example, first and second layers 454 and 456of chuck 404 can be a single integral layer defining voids 464.

In some embodiments, each of layers 450, 452, 454, and 456 is composedof one or more materials having ultra-low coefficients of thermalexpansion that vary as a function of temperature. For example, thematerial composing layers 450, 452, 454, and 456 can be ultra-lowexpansion silicon-based materials (e.g., ULE® glass manufactured byCorning), glass materials, ceramic materials, silicon-based glassceramic materials (e.g., ZERODUR® glass ceramic manufactured by SCHOTT),or a combination thereof.

An interface 458 between surface 418 of clamp 406 and surface 420 ofchuck 404 can be optically coupled. For example, in some embodiments, inwhich chuck 404 and clamp 406 are made of glass materials, ceramicmaterials, or silicon-based glass ceramic materials (e.g., ZERODUR®glass ceramic manufactured by SCHOTT), interface 458 can be an anodicbond. In some embodiments, in which chuck 404 and clamp 406 are made ofultra-low expansion silicon-based materials (e.g., ULE® glassmanufactured by Corning), interface 458 can be a fusion bond.

In some embodiments, first and second layers 450 and 452 of clamp 406and first and second layers 454 and 456 of chuck 404 are opticallycoupled to each other by anodic or fusion bonding. For example, firstand second layers 450 and 452 of clamp 406 can be fusion or anodicbonded together at interface 448, and first and second layers 436 and438 can be fusion or anodic bonded together at interface 446. Afterbonding, first and second layers 450 and 452 of clamp 406 and first andsecond layers 454 and 456 of chuck 404 are monolithic in someembodiments.

In some embodiments, second layer 456 of chuck 404 includes a pluralityof burls 462 that define a plurality of voids 464 as shown in FIG. 16.Although burls 462 in FIG. 16 have a trapezoidal cross-sectional shape,burls 462 can have other suitable cross-sectional shapes, for example, arectangular, triangular, or hemispherical shape. Similarly, althoughvoids 464 in FIG. 16 have a trapezoidal cross-sectional shape, voids 464can have other suitable cross-sectional shapes, for example, arectangular, triangular, arcuate, or circular shape.

In other embodiments, chuck 404 is a single layer defining voids 464. Insome embodiments, a vacuum is formed in voids 464. In some embodiments,the vacuum occurs during operational use of the lithographic apparatus.In other embodiments, voids 464 are filled with a thermally insulatingfluid, for example, air or any other insulating fluid.

Voids 464 decreases the thermal coupling (i.e., thermally isolates)between (i) first layer 454 of chuck 404 that is adjacent clamp 406 and(ii) second layer 456 of chuck 404 that includes voids 464, which inturn reduces thermal coupling between clamp 406 and chuck 404. Thisthermal insulation provided by voids 464 allows second layer 454 ofchuck 404 and clamp 406 to operate at temperatures substantially lowerthan room temperature or 22° C., for example, at temperatures below 2°C., while second layer 456 of chuck 404 maintains a temperature aboutequal to the temperature of chuck 404 at its undeformed, manufacturedstate, for example, about room temperature or 22° C. This configurationcan reduce residual thermal errors in chuck 404 while also improvingchuck stability and manufacturing.

In embodiments in which voids 464 are filled with a thermally insulatingfluid and/or in which fluid circulating channels 466 are optionallyformed in second layer 456 of chuck 404, the resulting thermal isolationfrom voids 464 allows for (1) a smaller temperature difference betweenthe fluids passing through channels 408 and voids 464 or channels 466,and/or (2) a smaller distance between channels 408 chuck 404, which canimprove scale stability and chuck flatness.

In some embodiments, channels 466 can be omitted from chuck 406. Becausevoids 464 thermally isolate chuck 404 from the portion of clamp 406 thatincludes channels 408, conditioning of chuck 404 via fluid flow inchannels 466 is rendered unnecessary.

In some embodiments, the surface area of burls 462 that interface withfirst layer 454 of clamp 406 is less than 50 percent the surface area ofthe surface of first layer 454 facing second layer 456 of chuck 404. Insome embodiments, the surface area of burls 462 that interface firstlayer 454 of chuck 404 is less than 10 percent the surface area of thesurface of first layer 454 facing second layer 456 of chuck 404.

In some embodiments, the temperature of fluid flowing through channels408 of clamp 406 (and channels 466) is controlled as described in anyone of the described embodiments of this application.

Example Embodiments of Object Temperature Control Methods

In use, any of the above embodiments of support 400 can control atemperature of object 402 held by clamp 406, which is coupled to chuck404 of a lithographic apparatus. For example, in some embodiments, amethod of cooling object 402 using clamp 406 and chuck 404 includesexposing object 402 with radiation beam 403. In some embodiments,exposing object 402 with radiation beam 403 is part of the process ofmanufacturing ICs. For example, exposing object 402 with radiation beam403 includes exposing a reticle with radiation to impart a pattern onthe radiation beam.

The method of cooling object 402 using clamp 406 and chuck 404 includescan also include conditioning a temperature of a first portion of clamp406. For example, the temperature of a portion of clamp 406 havingchannels 422 and surface 418 coupled to a surface 420 of chuck 404 canbe conditioned by passing fluid at a first temperature, for example,about 22° C., through channels 422. The method can also includeconditioning a temperature of a second portion of clamp 406, forexample, a portion of clamp 406 having channels 408 and surface 416,holding object 402 by passing a fluid at a temperature lower than thetemperature of the fluid passing through channels 422 through channels408. In some embodiments, the fluid passing through channels 408 isconditioned to have different temperatures at different points in time.For example, before passing fluid through channels 408 at a temperaturelower than the temperature of fluid passing through channels 422, thefluid passing through channels 408 can be conditioned to have atemperature, for example, about 22° C., that is about equal to thetemperature of fluid passing through channels 422. In some embodiments,controller 413 can then transmit a control signal to fluid conditioningdevice 410 to adjust the temperature of fluid passing through channels408 from the higher temperature, for example, about 22° C., to the lowertemperature, for example, −8° C., as shown in FIG. 4. The change intemperature can coincide with the start of object 402 being exposed withradiation beam 403 as shown in FIG. 4.

In some embodiments, object 402 is loaded on clamp 406 while the fluidpassing through channels 408 is conditioned to have a temperature, forexample, about 22° C., that is about equal to the temperature of fluidpassing through channels 422.

In some embodiments, the method of cooling object 402 includesconditioning the fluid passing through channels 408 to have atemperature, for example, −8° C., that is less than a target averagetemperature, for example, about 22° C., of object 402 when exposed withradiation beam 403. In some embodiments, the target average temperatureof object 402 is about the zero-crossing temperature of the materialcomposing object 402.

In some embodiments, the method of cooling object 402 includesconditioning the fluid passing through channels 408 to have atemperature, for example, about −8° C., such that the cooling power onobject 402 generated by passing fluid through channels 408 is aboutequal to a heating power, for example, about 80 W, applied to object 402during exposure with radiation beam 403.

In some embodiments, the method of cooling object 402 includesconditioning the fluid passing through channels 408 to have atemperature, for example, about −8° C., such that generated internalthermal forces of object 402 when object 402 is being exposed withradiation beam 403 are substantially symmetric about an axissubstantially parallel with surface 414 of object 402. In suchembodiments, the sum of the internal bending moments in object 402 dueto the internal thermal forces is about zero. For example, fluid passingthrough channels 408 can be conditioned to have a temperature thatgenerates internal thermal forces as shown in FIG. 9.

In some embodiments, after object 402 is exposed with radiation beam403, the fluid passing through channels 408 is conditioned to have atemperature, for example, about 22° C., that is about equal to thetemperature of fluid passing through channels 422. For example, afterexposing object 402 to radiation beam 403, controller 413 can transmit acontrol signal to fluid conditioning device 410 to adjust thetemperature of fluid passing through channels 408 from the lowertemperature, for example, about −8° C., to the higher temperature, forexample, about 22° C. The change in temperature can coincide withcessation of object 402 being exposed with radiation beam 403.

Any one of the above described embodiments for controlling thetemperature of an object 402 and chuck 404 can be used to manufactureICs. For example, the object 402 can be a reticle used to impart apattern of one layer of an IC on radiation beam 403 that will be exposedon a wafer.

Although specific reference may be made in this text to the use anelectrostatic clamp in lithographic apparatus, it should be understoodthat the electrostatic clamp described herein may have otherapplications, such as for use in mask inspection apparatus, waferinspection apparatus, aerial image metrology apparatus and moregenerally in any apparatus that measures or processes an object such asa wafer (or other substrate) or mask (or other patterning device) eitherin vacuum or in ambient (non-vacuum) conditions, such as, for example inplasma etching apparatus or deposition apparatus.

Although specific reference may be made in this text to the use oflithographic apparatus in the manufacture of ICs, it should beunderstood that the lithographic apparatus described herein may haveother applications, such as the manufacture of integrated opticalsystems, guidance and detection patterns for magnetic domain memories,flat-panel displays, liquid-crystal displays (LCDs), thin-film magneticheads, etc. The skilled artisan will appreciate that, in the context ofsuch alternative applications, any use of the terms “wafer” or “die”herein may be considered as synonymous with the more general terms“substrate” or “target portion”, respectively. The substrate referred toherein may be processed, before or after exposure, in for example atrack (a tool that typically applies a layer of resist to a substrateand develops the exposed resist), a metrology tool and/or an inspectiontool. Where applicable, the disclosure herein may be applied to such andother substrate processing tools. Further, the substrate may beprocessed more than once, for example in order to create a multi-layerIC, so that the term substrate used herein may also refer to a substratethat already contains multiple processed layers.

Although specific reference may have been made above to the use ofembodiments in the context of optical lithography, it will beappreciated that the invention may be used in other applications, forexample imprint lithography, and where the context allows, is notlimited to optical lithography. In imprint lithography a topography in apatterning device defines the pattern created on a substrate. Thetopography of the patterning device may be pressed into a layer ofresist supplied to the substrate whereupon the resist is cured byapplying electromagnetic radiation, heat, pressure or a combinationthereof. The patterning device is moved out of the resist leaving apattern in it after the resist is cured.

It is to be understood that the phraseology or terminology herein is forthe purpose of description and not of limitation, such that theterminology or phraseology of the present specification is to beinterpreted by those skilled in relevant art(s) in light of theteachings herein.

The terms “radiation” and “beam” as used herein encompass all types ofelectromagnetic radiation, including ultraviolet (UV) radiation (e.g.,having a wavelength of or about 365, 355, 248, 193, 157 or 126 nm) andextreme ultraviolet (EUV) radiation (e.g., having a wavelength in therange of 5-20 nm), as well as beams of charged particles, such as ionbeams or electron beams.

The term “lens”, where the context allows, may refer to any one orcombination of various types of optical components, includingrefractive, reflective, magnetic, electromagnetic and electrostaticoptical components.

The term “etch” or “etching” or “etch-back” as used herein generallydescribes a fabrication process of patterning a material, such that atleast a portion of the material remains after the etch is completed. Forexample, generally the process of etching a material involves the stepsof patterning a masking layer (e.g., photoresist or a hard mask) overthe material, subsequently removing areas of the material that are nolonger protected by the mask layer, and optionally removing remainingportions of the mask layer. Generally, the removing step is conductedusing an “etchant” that has a “selectivity” that is higher to thematerial than to the mask layer. As such, the areas of materialprotected by the mask would remain after the etch process is complete.However, the above is provided for purposes of illustration, and is notlimiting. In another example, etching may also refer to a process thatdoes not use a mask, but still leaves behind at least a portion of thematerial after the etch process is complete.

The above description serves to distinguish the term “etching” from“removing.” In an embodiment, when etching a material, at least aportion of the material remains behind after the process is completed.In contrast, when removing a material, substantially all of the materialis removed in the process. However, in other embodiments, ‘removing’ mayincorporate etching.

The terms “deposit” or “dispose” as used herein describe the act ofapplying a layer of material to a substrate. Such terms are meant todescribe any possible layer-forming technique including, but not limitedto, thermal growth, sputtering, evaporation, chemical vapor deposition,epitaxial growth, atomic layer deposition, electroplating, etc.

The term “substrate” as used herein describes a material onto whichsubsequent material layers are added. In embodiments, the substrateitself may be patterned and materials added on top of it may also bepatterned, or may remain without patterning.

The term “substantially” or “in substantial contact” as used hereingenerally describes elements or structures in physical substantialcontact with each other with only a slight separation from each otherwhich typically results from fabrication and/or misalignment tolerances.It should be understood that relative spatial descriptions between oneor more particular features, structures, or characteristics (e.g.,“vertically aligned,” “substantial contact,” etc.) used herein are forpurposes of illustration only, and that practical implementations of thestructures described herein may include fabrication and/or misalignmenttolerances without departing from the spirit and scope of the presentdisclosure.

While specific embodiments have been described above, it will beappreciated that the invention may be practiced otherwise than asdescribed. The description is not intended to limit the invention.

It is to be appreciated that the Detailed Description section, and notthe Summary and Abstract sections, is intended to be used to interpretthe claims. The Summary and Abstract sections may set forth one or morebut not all exemplary embodiments of the present invention ascontemplated by the inventor(s), and thus, are not intended to limit thepresent invention and the appended claims in any way.

The present invention has been described above with the aid offunctional building blocks illustrating the implementation of specifiedfunctions and relationships thereof. The boundaries of these functionalbuilding blocks have been arbitrarily defined herein for the convenienceof the description. Alternate boundaries can be defined so long as thespecified functions and relationships thereof are appropriatelyperformed.

The foregoing description of the specific embodiments will so fullyreveal the general nature of the invention that others can, by applyingknowledge within the skill of the art, readily modify and/or adapt forvarious applications such specific embodiments, without undueexperimentation, without departing from the general concept of thepresent invention. Therefore, such adaptations and modifications areintended to be within the meaning and range of equivalents of thedisclosed embodiments, based on the teaching and guidance presentedherein.

The breadth and scope of the present invention should not be limited byany of the above-described exemplary embodiments, but should be definedonly in accordance with the following claims and their equivalents.

What is claimed is:
 1. A lithographic apparatus comprising: a clampconfigured to receive an object and comprising: a first layer includingat least one first channel arranged to be adjacent to the object andconfigured to pass a first fluid at a first fluid temperature, a thirdlayer including at least one second channel configured to pass a thirdfluid at a third fluid temperature, and a second layer sandwichedbetween the first layer and the third layer, the second layer includingat least one void configured to thermally insulate the at least onefirst channel and the at least one second channel; and a chuck coupledto the third layer of the clamp.
 2. The lithographic apparatus of claim1, wherein the at least one void is at a vacuum.
 3. The lithographicapparatus of claim 1, wherein the at least one void is filled with asecond fluid.
 4. The lithographic apparatus of claim 1, wherein the atleast one void comprises a plurality of voids.
 5. The lithographicapparatus of claim 1, further comprising a fluid conditioning deviceconfigured to change a temperature of the first fluid.
 6. Thelithographic apparatus of claim 5, wherein the fluid conditioning deviceis configured to change a temperature of the first fluid from a secondfluid temperature to the first fluid temperature.
 7. The lithographicapparatus of claim 6, wherein: the fluid conditioning device isconfigured to change the temperature of the first fluid from the secondfluid temperature to the first fluid temperature when the object isbeing exposed with radiation, and the second fluid temperature isgreater than the first fluid temperature.
 8. The lithographic apparatusof claim 6, wherein the first fluid temperature is in a range from about−15° C. to about 15° C., and wherein the second fluid temperature is ina range from about 17° C. to about 27° C.
 9. The lithographic apparatusof claim 1, wherein the first fluid temperature is less than a targetaverage temperature of the object when the object is being exposed withradiation.
 10. The lithographic apparatus of claim 1, wherein: theobject comprises a material having a coefficient of thermal expansionthat varies as a function of temperature; the coefficient of thermalexpansion of the material of the object is about zero at a zero-crossingtemperature of the object; and the first fluid temperature is such thatan average temperature of the object when the object is being exposedwith radiation is equal to about the zero-crossing temperature of theobject.
 11. The lithographic apparatus of claim 1, wherein the firstfluid temperature is such that internal forces of the object when theobject is being exposed with radiation are substantially symmetric in adirection perpendicular to a surface of the clamp holding the object.12. The lithographic apparatus of claim 1, wherein the first fluidtemperature is such that a sum of the internal forces of the object whenthe object is being exposed with radiation is about equal to zero. 13.The lithographic apparatus of claim 1, wherein the at least one firstchannel comprises a plurality of first channels, and wherein the objectis a patterning device.
 14. A method for controlling a temperature of anobject held by a clamp of a lithographic apparatus, the methodcomprising: exposing an object with radiation; passing a first fluid ata first fluid temperature through at least one first channel defined bya first layer of the clamp to condition a temperature of the first layerof the clamp; passing a third fluid at a third fluid temperature throughat least one second channel defined by a third layer of the clamp tocondition a temperature of the third layer of the clamp; wherein theclamp includes a second layer sandwiched between the first layer and thethird layer, the second layer including at least one void configured tothermally insulate the at least one first channel and the at least onesecond channel, wherein the third layer of the clamp is coupled to achuck.
 15. The method of claim 14, further comprising: before passingthe first fluid at the first fluid temperature through the at least onefirst channel, passing the first fluid at a second fluid temperaturethrough the at least one first channel to condition the temperature ofthe first layer of the clamp; and after passing the first fluid at thesecond fluid temperature through the at least one first channel,changing the second fluid temperature of the first fluid to the firstfluid temperature of the first fluid, wherein the second fluidtemperature is greater than the first fluid temperature.
 16. The methodof claim 14, wherein: the first fluid temperature is conditioned to bein a range from about −15° C. to about 15° C.; and the second fluidtemperature is conditioned to be in a range from about 17° C. to about27° C.
 17. The method of claim 16, wherein: the first fluid temperatureis conditioned to be about −8° C.; and the second fluid temperature isconditioned to be about 22° C.
 18. The method of claim 14, wherein thefirst fluid temperature is conditioned to be less than an averagetemperature of the object when exposing the object with radiation. 19.The method of claim 14, wherein: the object comprises a material havinga coefficient of thermal expansion that varies as a function oftemperature; the coefficient of thermal expansion of the material of theobject is about zero at a zero-crossing temperature; and passing thefluid at the first fluid temperature through the at least one channelgenerates an average temperature of the object when exposing the objectwith radiation that is equal to about the zero-crossing temperature ofthe material of the object.
 20. A clamp configured to be arranged in alithography system to receive an object, comprising: a first layerincluding at least one first channel arranged to be adjacent to theobject and configured to pass a first fluid at a first fluidtemperature, a third layer including at least one second channelarranged to be adjacent to a chunk and configured to pass a third fluidat a third fluid temperature; and a second layer sandwiched between thefirst layer and the third layer, the second layer including at least onevoid configured to thermally insulate the at least one first channel andthe at least one second channel.
 21. The clamp of claim 20, wherein theat least one void is at a vacuum.
 22. The clamp of claim 20, wherein theat least one void is filled with a second fluid.
 23. The clamp of claim20, wherein the at least one void comprises a plurality of voids. 24.The clamp of claim 20, wherein the at least one first channel isconnected to a fluid conditioning device configured to change atemperature of the first fluid.